Posted
by
samzenpus
on Wednesday June 11, 2014 @06:44PM
from the take-me-to-your-leader dept.

First time accepted submitter sayhem (1842674) writes Various explanations for why we don't see aliens have been proposed—perhaps interstellar travel is impossible or maybe civilizations are always self-destructive. But with every new discovery of a potentially habitable planet, the Fermi Paradox becomes increasingly mysterious. There could be hundreds of millions of potentially habitable worlds in the Milky Way alone. This impression is only reinforced by the recent discovery of a "Mega-Earth," a rocky planet 17 times more massive than the Earth but with only a thin atmosphere. Previously, it was thought that worlds this large would hold onto an atmosphere so thick that their surfaces would experience uninhabitable temperatures and pressures. But if this isn't true, there is a whole new category of potentially habitable real estate in the cosmos.

Well, it is always possible we are simply the first. We do have an unusually old population I star and it still took billions of years for humans to come on the scene, so it is possible that the typical case simply takes longer and many suns are younger then our's.

You know what? All very nice, but how about this? We are not all that interesting, nor special, and in the last 35,000 years when we could comprehend what we're looking at, no-one's bothered to swing by and ask for a cup of sugar.

It may also be possible that we are part of a nature preserve, or that there are more than enough planets with similar conditions to inhabit, to not have to displace or destroy an entire culture.

Another possibility is that we're left alone, because other civilizations have been contacted before, and once given technology, have self immolated themselves akin to giving firearms to the natives.

That, or we're won the interstellar lottery, and we are indeed the first who will learn a lot of lessons as we swarm across the galaxy once we figure out how to get off this damn rock.

It may also be possible that we are part of a nature preserve, or that there are more than enough planets with similar conditions to inhabit, to not have to displace or destroy an entire culture.

I've been told off for proposing the nature preserve idea. Various arguments were that the aliens would need a 'huge fleet' to stop colonization efforts from reaching our system, that we'd notice our neighboring systems are inhabited, etc...

They didn't have a good response to my point that our radio reception efforts have been primitive enough that in order to 'hear' Alpha Centari the aliens would need to deliberately transmit an easy to intercept radio signal at us using several GW of power using the best dish technology we have.

The Earth, at it's loudest(digital technology is actually making us 'quieter' on the interstellar scene), wouldn't be 'heard' by the Arecibo Observatory at distances over a light year.

In short, I don't see an alien civilization beaming GW level signals at prospective systems more or less continously for millions of years in the vague hope that we'll notice and answer back. Meanwhile, we've been able to 'listen' for the equivalent of not even an eyeblink.

Eh, whatever. My other pet theories are that by the time a civilization is capable of colonizing other solar systems it's either become too insular to want to bother(you give up a LOT going to another solar system), or so adopted to space that colonizing planets is no longer a thing. Which makes 'nature preserve' for potentially life-bearing planets, cradles for new civilizations, not an expensive strategy at all.

That's of course assuming they even use radio or other em radiation based systems we'd even recognize as communication.If you want me to tell you what they might use, I would have to first reply with a question, "If you could talk to someone a thousand years ago, and you asked them how would people a thousand years in the future communicate at long distances with each other, and what do you think their answer would be."Although we can speculate in a limited and fanciful way regarding unknown technologies as

Various forms of the "downer hypothesis" are quite plausible, but I find the "adapted to space" hypothesis equally plausible. Also the "insular" hypothis has a lot going for it. Move away from the home system and your latency really increases. Additionally there's the "we become pets" scenario, where we end up just being kept as "pets" by the computerized intelligence(s) that run the system. Another possibility is that space travel is just too deadly for organic life...though in that case you'd expect t

So far, we have precious little evidence one way or another about this. Lots of people make up all sorts of numbers for the Drake equation, but frankly it's almost entirely speculation. There seems to be this assumption nowadays that life will inevitably evolve on planets with similar conditions to Earth, but how do we possibly know that? What counts as sufficiently "similar"?

Go back before Carl Sagan and a few other such scientists, and the idea that the cosmos was littered with life was treated only by imaginative science fiction writers -- the presumption that something like SETI should turn up something would have been seen a little weird, certainly not based on any scientific evidence.

And what evidence exactly have we accumulated since then? Other than 40 years of Star Trek finding civilizations everywhere, do we have anything scientific to base our estimates on?

No. Not really. In particular, while there has been some work in self-organizing systems and theories about how we get from basic amino acids to the first "living" cells, there's a whole lot of steps to fill in to explain how life begins.

And frankly, until we sort that out, let's just not pretend we're doing anything other than speculating from a single data point -- which means we have absolutely no evidence at all to decide whether the universe is teeming with life in every star system, or whether the situation on Earth was so specific that we're alone (or nearly so).

These articles about the Fermi Paradox always bother me a bit because of this. There's nothing "scientific" about them. I'm not saying we shouldn't look for aliens (and it would be truly interesting if we found anything), but we simply have no clue whether life is likely to evolve on 1 in 10 planets or 1 in 100 trilllion planets. Until we find life somewhere else or we can figure out the details of how to manufacture it in a lab (and determine how likely such conditions are to occur naturally), this is all idle speculation. Thus, there's really no "paradox" to resolve, since the probability estimates are meaningless.

The problem with Drake's equation isn't the uncertainty - that's part of the assumption behind the equation. It's that it doesn't properly account for space & time. Let's say that the highest number is correct and that there are 100 million civilizations

In 4.6 billion year history of our solar system intelligent life has had the possibility of traveling to another star for 1.08695652e-8 of that time (that we know of anyway) - that means that of the 100 million civilizations less than 132 might exist at the same time and if distributed evenly would be 1 per 7.1969697e+15km of space. Meaning that our nearest neighbour might be 760 light years away. That means that if they just started transmitting at the same time we did, we won't pick them up for another 710 years. If they started 100,000,000 years ago those signals have long since passed us by and we likely don't have the science to pick up the more advanced signals that might be passing us by right now.

Intelligence sufficient to survive -- what evolution really pushed for -- is very low performance for us. Assuming another species will exceed the required baseline for survival may be an entirely unwarranted assumption. We don't know yet.

But in our case... we regularly produce *really* smart individuals. Almost incomprehensibly so as compared to that required for survival. We also figured out the scientific method and left hand-waving philosophy in its own backwater, staring at its navel, while science ac

Actually, many species have the potential of homo sapiens - with time, and without human presence, any one of the Primate order could eventually have risen in our place. We just got there first. One can't exclude the possibility of something like a dolphin or killer whale evolving to a land based intelligent creature. Your argument has the same problem as the Drake equation - it doesn't take into account time. Scientists estimate that there are 8.7 million species on earth and one can't have the ego to

That's 12 species, including homo sapiens, though homo sapiens killed off or absorbed the other 11 (remember, Homo sapiens are upto 30% Homo neanderthalensis due to interbreeding). Homininae are close enough genetically and many have shown the ability to communicate that they, given the lack of human presence, could evolve to our state as well. That's another 39 species.

Also, while you're taking the past into account you're not taking the future. In 4.6 billion years whether you want to say 1 to 12 species evolved depending on how you want to frame it. The Earth has an estimated 5 billion years remaining... so lets say in the next 100 years, even a million years, there's an extinction event and primates all die. That's 4.9 billion years for another intelligent species to develop.

This has not happened once, it's happened multiple times in the Homo genus

None of those species developed the kind of representational, specifically human intelligence that builds spaceships and discovers universal gravitation. They "could have", of course, but as a poster up this thread has pointed out, we have left the hand-wavey philosophy behind and are now using the only way of knowing: the discipline of testing ideas by systematic observation, controlled experiment and Bayesian inference... this discipline is called "science".

Can you definitively say that the genes responsible for intelligence come from the Homo Sapien line or do they come from the 30% of Homo neanderthalensis? (they did have a larger cranial capacity) Maybe they were the smart ones and we were simply more aggressive/faster breeding/hardier species. Maybe the "genius" gene comes from a tiny bit of Denisova hominin DNA and the reason there aren't more Einsteins is because it's a rarer recessive gene... or it could be none of that. It's not unreasonable to posi

Fermi's Paradox makes one major assumption: "the tendency to fill up all available territory seems to be a universal trait of living things"

This is a false assumption. While most species that come into an area that can sustain them tend to rise to 120% of the sustainable population then die back to 80%, humans do not follow this pattern. We've concentrated ourselves and while we've spread over a huge portion of the planet there's one curious thing that happens: the birth rate decreases with education:

Not a popular thing to say around here, but that's what this speculation about alien life comes down to for those on the side of 'it exists': it's a religion, with SETI as its High Mosque, and the Drake Equation its shahada [wikipedia.org]

. Those who come down on the side of 'it might be possible' are the equivalent of the Christmas-only Christians.

Or maybe the universe is so competitive that anyone who announces their presence eats the bad end of a relativistic weapon.

Who knows - maybe one's already headed for Earth. It's not like we have been hiding our radio transmissions or anything. Sure would be naive of us to assume aliens are all sunshine and rainbows and want nothing more than to love and hug us. Now granted, I think if relativistic weapons flying about were a real issue, we'd probably have seen evidence for it in the universe by now, but anyone who ascribes benevolence to aliens is just a fool ignoring every lesson nature has taught us on this planet.

Personally, I'm against alien contact unless it's US doing the contacting. The kind of power-play dynamic where we're met by aliens only puts us at a serious disadvantage. We're basically blind right now. We need to stay silent, open our eyes and ears, and see what happens around us a little before we go shouting to the galaxy at large "Hey! Over here!"

I think the only comforting fact about it all is that our biodiversity is probably the rarest thing about our planet - so if there is any value in that, any conquerors will at least leave our biosphere intact.

Or maybe the universe is so competitive that anyone who announces their presence eats the bad end of a relativistic weapon.

This is a reasonable fear - and the problem is unless you are sure the universe isn't that competitive, it actually makes sense to assume it is. Because it's not hard to build a relativistic weapon your target would never see coming, and would wipe them out with one hit. (And we wouldn't see much evidence of them out there, even if they were fairly common - they look like any other floating rock, really.)

So the moment you announce yourself you could become a target for an unknown assailant who will kill y

Well, it's been less than a century since we started broadcasting our existence as a technological species to the cosmos, the signals have only had a chance to reach a few hundred other planets so far. And through an accident of evolution our atmosphere was flooded with toxic oxygen early on. It's quite possible that any alien astronomers would have glanced at our world and thought "Whoa - an oxygen atmosphere, that's weird. What sort of hellish fire-stormed world do you imagine *that* would make for? Well, we're not going to find any life there, make a note in the logs and lets keep looking for more promising candidates."

Not to mention the fact that even if we had an identical twin Earth around Alpha Centauri, one of our nearest neighbors, it's unlikely that we could detect their transmissions with our current radio telescopes - they would be lost in the much louder radio noise of their star. So I think it's still a little premature to assume there's any paradox at all. Technological civilizations could be orbiting practically every star in the galaxy, and unless one of them when out of their way to contact us (or someone else in the same line of transmission) we would have no idea they were there. Hell, we're barely beginning to reach the point where we could detect massive engineering projects like a Ringworld around even the nearest star

We are not all that interesting, nor special, and in the last 35,000 years when we could comprehend what we're looking at, no-one's bothered to swing by and ask for a cup of sugar.

Or it could be that interstellar travel is just extremely expensive, so that any aliens civilizations that exist either don't bother, or they can only afford to visit a small number of places (and we're way down the list), or they can only send extremely small (read: hard-to-notice) spacecraft.

Until we invent something like a Warp Drive (or at least discover a reason to think such a thing might be possible even in principle), I'm inclined to prefer this explanation, at least over the 'nature preserve' idea:)

The chances of advanced technological lifeforms developing is nearly infinitely small, and the distances between the ones that actually do develop are so great, that they never contact or even become aware of each other. Life forms on earth that are far in advance of humans are based on intelligence that evolved into post-biological form before one of the 100 million year cycles that periodically destroys all life on earth.

And they very nicely cleaned up the place spic and span so we wouldn't find the slightest trace of them, unlike the literally thousands of fossils that are much older from much smaller and imprintable.

We weren't the first complicated life here. It took several mass extinctions, but then humanity as we know it took around 300,000 years to evolve from the ancestor primates, give or take a few million to get from the single-cell stage.

So sans a few mass extinctions, someone would've been here are a lot sooner - and the Earth is 4 billion years old and we know planet formation doesn't seem to take that long.

So given the size of the universe, we know from just here that there's definitely been life and intelligent life favorable conditions elsewhere just from the limited sample set we've collected. What we don't know is what happens to it - what's the "main sequence" behavior of technological civilizations like ours? What do they become?

Of course, it's also entirely possible we actually are in particularly well governed galaxy and everyone is staying out of our way till we reach out and make first contact. Then we'll find out that Galactic Resolution 8A prohibited the international broadcasting of luminal RF in our direction or something.

So given the size of the universe, we know from just here that there's definitely been life and intelligent life favorable conditions elsewhere just from the limited sample set we've collected.

[Citation needed.]

Until we have any actual evidence of life or intelligent life "elsewhere," we have absolutely no evidence that conditions "elsewhere" are sufficiently "favorable" for anything. It's all just speculation. The "sample set" is ONE instance, which is not statistically significant evidence for anything.

"Favorable" could be 1 in 10 planets, or it could be 1 in 100 quadrillion quadrillion. You can't conclude anything from a sample size of 1.
(There's also not a lot of evidence AGAINST favorable conditions existing elsewhere, since we really can't know what "favorable conditions" are until we've enlarged our sample set, but that doesn't mean anything either.)

The old biology rule is: if you have a sample of one, you make the assumption that it is "average."

But more on point, people who suggest there's no reason to think that there isn't other places in the universe with life tend not to understand how truly fucking huge the universe is.

There are 88 objects (known) in our solar system larger than 200 miles in diameter. We know one has life, we believe 3 others have a promising chance to have life (Enceladus, Titan. Europa), as well as the possibility of subt

The old biology rule is: if you have a sample of one, you make the assumption that it is "average."

Yes, I'm very familiar with this assumption. In exobiology arguments it's known as the principle of mediocrity [wikipedia.org].

The problem is that it's simply an assumption. It can be wrong. We simply don't know. Moreover, in biology this often makes a little more sense when you're, say, dealing with a single fossil specimen or something. In that case, you're at least dealing with an interdependent ecosystem of life, and based on evolutionary principlles, most specimens we encounter are likely to be ones that survived and multiplied and existed as species with more than one exemplar.

There's no such data or evidence for extraterrestrial life, because we're not part of a common ecosystem with known evolutionary principles. Again, we have just one data point.

There are 88 objects (known) in our solar system larger than 200 miles in diameter. We know one has life, we believe 3 others have a promising chance to have life (Enceladus, Titan. Europa), as well as the possibility of subterranean life on Mars (methane venting).

Based on what, exactly? A whole truckload of assumptions about how common life MUST be and what conditions make it LIKELY. But we have no evidence for most of those assumptions. Call me when you find life on one of those places with a "promising chance" -- then we'll have EVIDENCE to talk about and more than one data point. Until then, this is idle speculation.

So lets do some math.

There's only one number that matters: P (chance of life evolving on a random planetary body).

Do you know that number? I certainly don't. You can make a bunch of stuff up about how "unique" or "not unique" the Earth is, but you simply don't know.

You do the math on how many objects that are out there. Again, anyone who doesn't think the odds are there's any life out there don't understand how fucking big an "out there" it is.

The universe could have 10^100 planets in it that are earthlike, but it wouldn't mean crap about finding life if P (chance of life evolving on a random planetary body) is 10^200. You still can't estimate a probability from one data point.

This all reminds me of a discussion in Richard Dawkins's Blind Watchmaker. He talks about how unusual it would be for four players to simultaneously get a royal flush in poker (or something like that). And then he says -- let's imagine some creatures that lived for millions of years (I can't remember the exact amount, but he gives something more specific). And he then concludes -- with all that time playing poker, these creatures would obviously not find it unusual if they all drew royal flushes at the same time occasionally.

It's a fun argument, but just for kicks I actually ran the numbers, and it turns out that Dawkins was off by many orders of magnitude for the lifespans of these creatures in order for this occurrence to be likely for them to experience.

Dawkins was obviously being sloppy there, and I don't fault him a lot for it since he was just making a casual analogy -- but his flawed methodology is PRECISELY what you are doing here. He simply assumed, "Yeah -- creatures who live millions of years" and assumed the numbers would make it likely for the poker hand to show up. Except the number that matters is P(weird poker situation), and he obviously didn't bother to compare that to his hypothetical giant lifespans of these long-lived poker-playing creatures.

It doesn't matter how big the numbers are for things in the universe. What matters is the chance of life evolving. Do I think it's likely we're unique in the universe? Well, if I had to state my BELIEF, I'd say "no." But that's NOT SCIENCE.

Science says we have one data point, and there's nothing else to extrapolate fro

We're the first technologically intelligent life here. Which is odd in itself. There are other biological features that have independently evolved multiple times: fins, wings, eyes...

If intelligence is such a huge advantage, why has been so rare, even on a planet where life is abundant? Maybe intelligence isn't such a great evolutionary advantage when weighted against its disadvantages. Maybe humans are a fluke where sexual selection got carried away in era with

Are you sure about that? As I recall our sun is believed to be a relative latecomer among third-generation stars, born roughly halfway through the period in which such stars are expected to form. There should be more stars out there with a similar element mix that were born before ours than after, and many, many of those stars would have been around long enough that life on them could have reached our current level of development before our star had even formed.

Unlikely.There is so much a water and other elements key to life as we know it that have been floating around for billion of years.

Unlikely? How can you know that?

What's the probability of life beginning in the first place?

What's the probability of life becoming complex?

What's the probability of sentience evolving?

There's no reasonable way to know what those probabilities really are. The only way to even get to the question is for all of them to have happened.

And the fact that it took about 1/2 the lifetime of our Sun for them to happen could very well be an indicator that all three aren't very likely at all to happen before the sun's life runs its course for any other habitable planet.

All stars and stellar generations are not the same. As the Universe ages, every generation of supernovae introduces more metals (which in astro means 'anything except hydrogen and helium') into the galactic medium. Stars significantly older than our sun are unlikely to have had enough metals to form lots of rocky planets. Or if they did, any intelligent life there would find many of the metals that we consider fairly rare to be virtually nonexistent.

Conversely, in the far future when a large fraction of the ISM is heavier elements, the freak exception will the formation of rocky worlds small enough that the inhabitants on their surface can escape into space at all...

And our star has lots of heavy elements circling around it, much of which make up our own planet, and those heavy elements came from the life cycle of the stars that came before us. Is that process necessary to support the chemical complexity of intelligent life? We don't know yet.

You are right. We don't know for sure.But a large variety of elements with fundamentally different properties (different masses, different chemical bonding properties) yields a large vocabulary of different molecules with widely differing properties. This large vocabulary of structure allows for a large vocabulary of function, increasing the number of ways in which self-sustaining reaction groups (and eventually life) could occur.

Which is utterly irrelevant to GP's point that we don't have the foggiest idea what the odds are of life arising. Our single, solitary sample isn't statistically significant.

There are several steps from amino acids to space-faring civilizations, and even active attempts by our best scientists haven't been able to get past step 1 in a controlled lab.

And in our one sample of life on Earth, we don't have any evidence in all of Earths history, of any of the steps happening TWICE, independently. Instead, it's all a nice, neat, clean, singular and unbroken, tree.

I don't know how likely it is, and NEITHER DO YOU. We have no idea what values belong in that part of the Drake Equation, and they could each/all conceivably be astronomically large.

Well, as has been pointed out before, just because life appears to stem from one thing, doesn't mean there wasn't a "Second Genesis" (or multitudes of them, even happening today). However, those other lifeforms have to compete for the same resources as better adapted ones (per natural selection). And then there are things that are "arguably life" that seem awfully close to life and awfully orthogonal to the existing tree, like viruses.

But besides that, what amazes me is that we are not only the most intelligent life on earth (for some values of intelligence), but as far as we can tell, the most intelligent life to have ever developed on earth.

This seems odd, given that there are so many other intelligent life (but nowhere near our level) like cetaceans, some birds (which are descended from Dinos, which had a longer time to evolve in interesting forms- not like early, ratlike mammals, to boot), other primates, some species of octopuses, and I am sure I can think of more examples.

Maybe the trick is having a big brain and a body plan that is flexible enough to do many things, starting with a high metabolism. I would think that a therapod with human intelligence levels would have an awfully hard time building spaceships.

And the brain consumes a lot of energy, which is why human muscles are relatively weak and energy efficient (also for endurance).

In that sense, it is my opinion that life is probably common, but intelligent life is rare, maybe even extraordinary, and probably not inevitable for a planet or system.

However, those other lifeforms have to compete for the same resources as better adapted ones (per natural selection).

It's dogmatic to assume some new life-forms would be out-competed by the existing ones. It's certainly one possibility, but completely unproven. It's just as possible they'd be orthogonal to existing biology, having highly different requirements, or developing in an area with ample resources. We wouldn't have fossil fuels if natural selection was perfect at developing life-forms that would

Have you ever watched one of those crazy shows purporting to show "evidence" of "Ancient Aliens" or some other such thing?

What's your opinion of them? Nonsense? Sensationalist?

If intelligent life evolved before humans, and became able to use tools like humans, any evidence they left behind wouldn't be taken seriously. Additionally, what may have been created by intelligent species might not clearly not be a natural phenomenon. For instance, what does a dinosaur's house look like? Even if you found a fo

Out to the geostationary orbit? Not in the last 3.9 billion years. That is 350 times farther out than the limit of space. Anything that removed everything in that bubble would have killed all life on earth. The only event of that magnitude that we have evidence of created the moon.

One detail you miss is that when each step happens once, it reduces the probability of the same kind of step happening again locally, because the first occurrence is a competitor for the would-be second, and has a time advantage to have evolved to be a better competitor, or an assimilator. Remember, life is about pattern competition, and pattern amalgamation (if more effective than competition at prolonging the sub-patterns.)

Life is about information patterns competing with each other to pattern the matter and energy which both surrounds and hosts the information.

Probably quite likely to happen, so long as there is enough structural and functional vocabulary (molecular variety and molecular combination variety) for embodied information to have probable mechanisms for enacting their 3D printing. Oh and just enough thermodynamic free energy and gravity so that stuff comes together about as often as it blows apart. Oh and another probable requirement is a region (such as but not exclusively) Earth's surface region, where common elements exist in all three of gaseous, liquid, and solid form and can sometimes transition in phase. This latter condition is again part of ensuring there can be enough structural and functional vocabulary to make the mechanisms (containment in solid or semi-solid structure, flow of energy-transferring and material-transferring contained gases and fluids.)

One could also argue that is it in fact bacteria that are evolutionary most successful organisms on earth.

That is a misleading statement. Humans are a single species. 'Bacteria' is a ridiculously large set of species, with each of them being adapted to quite a specific environment.

In addition to that, they will never be able to actively prevent their own extinction on a solar or galactic level, nor will they be able to actively spread on those levels. They might by chance, but not actively.

We spread across the entire planet long before we were technologically advanced. I would call that fairly successful. Intelligence allowed us to adapt the environment to our needs instead of the other way around.

What seems plausible to me is that habitable planets are overwhelmingly common, while spacefaring races are relatively rare such that there are millions or billions of habitable planets in the Milky Way, and perhaps only a few thousand spacefaring civilizations. Therefore, there is no 'need' for spacefaring aliens to colonize earth as there is an abundance of other inhabitable worlds out there and the chance that a spacefaring civilization happens to be close enough to us that we happen to be on their colon

Really, most of our broadcasts are now directed back towards earth via satellites, and any signals sent to space are of such a low intensity and so absurdly directional that the odds of it being detected are minuscule at best even with extremely sophisticated equipment sitting on the moon.

That isn't to say that we can't *also* talk into space, but we have gone to highly directional, low powered communications systems as our primary means of communications as a species. Even AM, FM, VHF, UHF, and various Cellular transmissions are now directional and positioned in a longitudinal configuration to reduce power waste by broadcasting where people won't be (strait up).

During the 50's and 60's, sure... we were broadcasting some very powerful signals into space simply because we as a civilization were trying to be as loud as possible to hit every inch of our planet. During that point in time, there is a chance that another culture, if they were of sufficient technological advancement (about where we are today or ahead of it) that they *could* have seen us if they were specifically surveying our star and it's planets.

The bottom line is that like everything, intensity of any signal falls off at the square of the distance, and we are taking some major distances here. While those signals would be severely disrupted by the Oort Cloud, one would still see a deviation from the Cosmic Microwave Background Radiation as well as that of our star.

And we didn't give a species like us much time to find us.
And as long as we are talking like that, is it reasonable to also make a logical jump that a species that would have developed technologies necessary to detect us would have also implemented similar efficient means of communications for their species, as a result making them "less detectable" in a similarly short window?

The fact that an antenna is 9db or 30db higher in one direction quickly becomes irrelevant with the vast distances of space. Antennas don't work like flashlights. They are more like a light bulb with a two-way mirror on one side that reflects 50% of the light and lets 50% of it through out the back. At VHF and above, things like mountains act like mirrors that reflect signals straight up (among other directions), as well.

You are somewhat wrong about AM... at least broadcast band AM is mostly only directional in the sense that there's dead zones straight off the ends of the dipole. They are shooting quite a bit of signal upward. Our ionosphere does strongly reflect and attenuate what would make it out to space in those bands though.

This goes toward your comment about the 50s and 60s... we have far more powerful transmitters in operation now (some VHF TV the better part of 1 megawatt!), and in bands that aren't reflected by the ionosphere. If anything we are getting louder and louder.

Unfortunately the first thing they might see of humanity is free-to-air broadcast TV, and just assume that we are all complete idiots.

The problem is that the power of the signal very rapidly went down (in 1/R^2) so even when we were broadcasting in the 50ies-60ies, our best signal did not even go beyond 1 light year before being indistinguishable from noise , in the best case scenario (actually probably much less depending on the signal). There are only 2 signals which went beyond the 1 or 2 LY, and those were intentional "we are here" signal, sent toward M10 i think (or was it M52?) and those signals were maybe a few dozen minutes all combined together.

We would not be able to detect ourselves if we were located on our direct neighbor, 4 LY away, alpha centauri. By that point even our most powerful unintentional signal is beyond the noise floor (again except those few dozen minutes TOTAl over all our whole civilization time).

It's meaningless.Space is REALLY BIG. In fact, space s bigger than time is long.You could have started sending out robots 12 billion years ago and they wouldn't have even made a scratch in colonizing the universe.

Maybe travel at the speeds necessary to reach other star systems is impossible, and there ARE a TON of civilizations out there. But, they're all talking on some type of communication form - like Quantum CB or something - that we haven't discovered quite yet.

One day we will, and we won't make first contact with ONE species that day. We'll meet millions.

this makes a lot of sense to me. Given that EM radiation only travels at the speed of light, and falls of with the square of the distance, it is the cosmic equivalent of writing a letter, stuffing it in a bottle, throwing it in the ocean and hoping that your friend in Japan gets it. We think we are clever monkeys, but we are in effect beating on a log with a stick, when the rest of the universe is likely sending data packets via the cosmic version of fiber optic.

Or even just via tightbeam radio - it would have to be be a frelling LOUD signal to be heard over their own star's radio noise after all, and power radiated in any direction other than directly at their target would be completely wasted. Or if they had worked out a way to receive the signal through the noise, then there's no reason to believe we could hear it even if it were aimed right at us.

Maybe travel at the speeds necessary to reach other star systems is impossible,

50% of light-speed would get you to the next solar system, in the same time it would take to get a university degree. From there, you or your offspring can choose to try again, and see what's on the next one.

You don't need exotic technology to colonize the universe... only if you want to jump from one to the next as easily as you visit your relatives, in fine, Hollywood-movie fashion.

This was already considered in the Fermi Paradox. It's fascinating to see how many people here obviously don't know it, yet are happy to chime-in on the subject.

and there ARE a TON of civilizations out there. But, they're all talking on some type of communication form - like Quantum CB or something - that we haven't discovered quite yet.

We're already on the verge of manipulating the heavens, moving small bodies where we want them. Where's the astronomical observations showing planets stacked-up in spots they couldn't possibly get-to, naturally? Where's the data showing a large dark, low-mass object, that could possibly be a Dyson Sphere? If there's lots of somebodies, more advanced than us out there, there should be some physical evidence that's practically visible from here.

Or maybe we're just the only ones here.Or maybe aliens have their own shit to worry about.Or maybe they're already among us.Or maybe nerds should stop wasting their time wanking off about shit for which their is zero evidence - for, or against - and trying to derive concrete meaning from it.

I fully expect and eagerly anticipate the day we make first contact (hopefully without subsequently getting blown to shit, enslaved, whatever). But I'm also sensible enough to realize that no amount of masturbatory theo

Or maybe humans already achieved interstellar travel then, being the warmongering destructive bastards we are, went out and destroyed every non-human intelligence they could find. Afterwards, being the warmongering destructive bastards we are, we turned on ourselves and blew ourselves back to the stone age.

At a certain point that starts looking like an attractive option. If NASA announced that they've managed to create a warp bubble, no matter how small, then I'd say the low hanging fruit is that aliens are in contact with certain elements of humanity and that this isn't widely known because a huge percentage of the world would freak the fuck out.

At Los Alamos, right around the time of the Fermi Paradox, everyone was agog at the green fireball phenomenon. One of the greatest collections of scientists ever assembled were pretty evenly split on the subject. Some though the the green balls of fire flying through the sky and changing direction as if being intelligently guided were some kind of secret earthly craft, while many other were certain they were extraterrestrial in origin. No one doubted they were real, however, and no one thought they were natural.

You don't really hear about this, but it's part of what started Fermi along the way towards his paradox.

As for the usual "OMG, nobody could keep that secret!" meme. Even if someone had 100% proof of alien encounters, the signal to noise ratio is assumed to be no signal and all noise. Someone could have been shouting the truth from the rooftops for forty years and nobody would care because they'd be lost in the din of people seeing little green men and anal probes.

Between "every civilization eventually kills itself" and a high level conspiracy to keep the world from shitting their pants at alien life, I'll pick the conspiracy. The fact that half of humanity isn't really ready to stop killing one another over five thousand year old superhero stories is kind of telling. Hell, half of humanity is confused by shoes.

If, as seems possible, the first civilizations in the galaxy arose billions of years ago, they presumably know about us, or at least our planet (as the galaxy can be inventoried in a billion years). If they cannot exceed the speed of light, they are also used to very long scale conversations and travel delays. My guess, and it is just a guess, is that they wait 5000 or 10,000 years before getting back to any new civilization, because that's how long galactic conversations take, and also to weed out the flash-in-the-pans; either way, we may have a while to wait.

As for where they are, "any sufficiently advanced technology is indistinguishable from astrophysics," so look around. As just one example, the spiral arms of the galaxy are more recent than the possible age of the first civilizations, so they might be engineering constructs.

The others have a pretty good idea what is going on on our planet from decades of radio and tv broadcasts. Nobody in their right mind would visit our dirt-ball with vicious and stupid people in abundance.

First off, forget Hitler's Munich Olympics broadcast, that's way to new. The most interesting thing about Earth is roughly half a billion years old, and that's its "unnatural" atmosphere. Our atmosphere shouts, "Life!" like nothing else. The stuff in our air just doesn't cohabit from ordinary chemical processes - it has to be maintained. Not as old, but still older than Hitler's broadcast is the sustained presence of pollutants in the atmosphere. This might suggest, "intelligent, if immature/foolhardy life."

We can almost see this kind of stuff with Kepler, though to get to this level of detail we use several instruments in parallel - Kepler is the first-weeder. We're nowhere near having interstellar technology, so any race that does will likely have commensurate technologies in other areas as well. Most notably, if you're going to travel far, you want to know which direction to go, and as much about your destination as you can. They would have tools that make Kepler look like a child's toy. They would know how interesting Earth is. Where that ranks us with respect to other planets in another question, but I'll bet it's not as bleak a prospect as some say.

Personally I think the presence of us on Earth has to do with it's "sufficiently interesting history", including the collision that formed the moon, several asteroid/comet strikes like the dinosaur killer, etc. Not to mention plate tectonics, the magnetic field that keeps the solar wind from blowing our atmosphere away, etc. Like I said, I think Earth would be on the short-list.

By the same token, I also think they would observe. Our society and existence are fragile enough, one big kick could easily topple the whole mess. Imagine a preemptive strike by one power to prevent another power from getting "the advantages of alien technology," etc. We're also pretty darned "memetically susceptible," and even allowing an alien idea to reach us might upset the apple cart.

Or as an alternative, perhaps the Catholic Church was right, and Galileo (and Copernicus) were wrong. If not the physical center of the universe, if we're all there is, perhaps the Earth is the philosophical center of the universe.

So:1 - We're all there is, perhaps to become the Progenitors, perhaps not.2 - There is other life, hasn't gotten here yet, may not bother, may not be able.3 - There is other life, observing us, careful to remain unknown - the Prime Directive.4 - There is other life, getting ready to invade/destroy us.5 - There is other life, in contact only with the Illuminati and Club of Rome.

Consider "the rock we are on." What makes this rock so interesting? In theory, there are lots of rocks out there like ours. If they're able to get to us, they've certainly been to other rocks and ours isn't all that special.

Consider "Us." I won't go off on humanities foibles, so the only interest in us would be biologically or sociologically. Biologically, they can just show up and take samples. Sociologically, we might be interesting, but introducing themselves would change us--which would sort o

We are just on the edge of being able to upload humans into the machine, and give everyone virtual reality. Once we achieve that, everyone can have anything they want, without needing to colonize or mine anything. Turn the moon into our Matrix supercomputer, upload everyone, and turn the Earth into a nature preserve. Once you have that set up and everyone starts cranking out game modules, why would you want to give that up to visit another star? You think the colony ship will support the latest VR's?

The technology doesn't even have to be as sophisticated as mind-uploading or lunar supercomputers. The first consumer-grade technology that adequately simulates sex will lead to an almost immediate population collapse. What remains of the human race after that might not have the means to maintain an industrial civilization.

The Rare Earth Hypothesis is still the strongest contender for the solution to the Fermi Paradox. Suppose that there are a hundred different conditions necessary for intelligent life to evolve. These could include basic requirements (like liquid water and protection from ionization radiation), up to more subtle components (like a moon that massive enough to cause tides or an axial tilt to create seasons). Until we have another data point for reference, any condition on Earth might be considered a necessary condition. If each of these conditions has an independent probability of 1 out 10 or less, then it very well could be that Earth is unique in the galaxy, possibly the the universe. The universe is big, but it is not 10^100 planets big.

So if we wanted to signal a civilization on the other side of the Milky Way (assuming we could muster the power), We would have to aim the focused radio beam on where that world would be in somewhere 50,000-100,000 years from now and they in turn would have to know the signal is coming and instantly reply to where we would be in another 50,000-100,000 years.

The whole communication thing is a total joke.

Any smart civilization would just want to make their world a nice place to live for as long as they could.

but four light years to the nearest star and 14,600+ stars within 100 light years. And by the way, we know EXACTLY where to point lasers (not foolish radio SETI) for stars at that distance to be detected.

our radio and television transmissions to date are too weak for our own tech to detect at 10 light years. and we're mostly using fiber and other lines instead of sattelites for comm as time goes on. what if they are a thousand years ahead of us, we can't detect a modulated beam of neutrinos or gravitons for example.

Various explanations for why we don't see aliens have been proposed—perhaps interstellar travel is impossible

Not only is interstellar travel possible, we've already done it (at least, we've sent 2 space probes outside our solar system which will eventually reach other stars). Interstellar travel within the lifespan of a single human being might be impossible, but enough other solutions exist (robotic probes, generational ships, suspended animation, long-lived alien species) that this limitation is n

My variant is that all, or almost all the civilizations the aliens know about formed around red dwarf stars. It's nice and stable there for very long periods of time. We're only stable here by luck - and our big moon helps some.

Another fun thing to think about: If you look at our system as a whole, from a very long distance, we look like we're still a pre-multicellular world. Sure, there's free oxygen and wate

Before diplomats from one country meet with diplomats from another country on Earth, they study everything they can about the situation and their counterparts. What if aliens are monitoring our communications to learn more about us -- what we do, why we do it, what we believe, how we're likely to respond to different scenarios, etc.? No one says that even if aliens came to Earth the first thing they'd do is find some schlub and say "Take me to your leader." Nor is it unlikely that a race capable of crossing the void between stars could hide from us, say by looking like a comet or asteroid.

Sufficiently advanced races who develop the technology to travel to other planets find that same technology eventually allows them to exit the universe entirely. This leads to custom universes that are far more suitable for stable permanent civilizations outside of the chaos of the original birth universe. Colonizing other planets just seems like a chaotic inefficient messy task with little reward.

I find it fascinating that everyone here feels that what they've come up with in 5 minutes is somehow new and unique, and going to add to the 65 years of professional interest in the Fermi Paradox. Many of whom confuse the question, because they don't even know Fermi's Paradox.

So here I present the full list of possible answers to Fermi's Paradox, that everyone here thinks they just came up with:

There are no old, space faring civilizations, for one inescapable reason. Technology is incompatible with species. No ifs or buts.

Brief explanation: Life of any kind, in any environment must always evolve as species - defined as multiple beings sharing a common 'genetic code base' - regardless of how the information is encoded. In our case it's DNA. In all species the individuals serve as reproductive vectors for the code they carry, and individual survival of the fittest is required for any species to evolve and adapt to its environment. This implies that individuals also die - this is necessary, otherwise natural selection cannot operate, hence no evolution.

Life is likely quite common in the Universe. Even if intelligence is statistically a rare development, there still should be countless instances, including plenty long ago, where 'long' means more than one star lifetime. So if intelligence results in technological cultures, including any kind of major engineering or space travel, where are they all? Even if such civilizations choose not to say hello to us, we should still see evidence of their works.But we don't. There's apparently nothing. Just elusive local UFO sightings, of unknown reliability. Certainly no daylight landings in city park, so to speak. That was just to restate the Fermi Paradox. Where is everyone? We exist, so there should be other civilizations like us, but much older and more technologically advanced.

The logical error here, is to assume that technology is a continuum; that a society develops technology and then just continues to progress as a society - a cooperating population of individuals with a common genetic heritage, hence species.

But this NEVER happens. Can never, will never, never does. Here's the inescapable reason.As a species develops technology, they inevitably discover the nature of the physical encoding scheme of their own biology. They develop the means to manipulate that coding scheme. Our fledgling genetic engineering is an example of how that starts. Quite rapidly the science of engineering their own coding will advance, since after all it's just a messy 'wet' version of computing science, and you can't have high tech without already being well advanced in computing technology.

Somewhere in the process of unraveling their genetic coding, an intelligent species will also develop a science of consciousness - what we presently think of as AI, but which is ultimately about minds in general and how they work, including our own.

As these two science threads advance, genetics and mind-science, it is 100% totally inevitable, that at some point individuals will gain the technological capability to begin modifying their own nature. We already do this - for instance using altered viruses to perform corrective edits of faulty DNA, eg the Cystic Fibrosis cure.But that is primitive stuff. Ultimately, gene engineering and AI technology provide individuals with the means to 'transcend' - to embark on total self re-engineering.

At this point in the analysis, most people become incapable of logically carrying through. It seems there's another strong cognitive bias or two, not listed in the Wiki. One is that most people seem incapable of thinking impartially about the probability of termination of their own species. Another is a mental block against thinking logically about the likely motivations of entities that do not share the species-centric world-view of us genetic humans.

Here's an idea: try thinking about an intelligent entity, that does NOT share any of our reproduction-motivated species-protective instincts. Nor any of the many cognitive biases in the Wiki list.Because that's what you get eventually, after any species-based individual achieves self-engineering capability, then immortality, an ability to deliberately optimize and enhance it's own mental capabilities, weed out instincts no longer appropriate to it's new existence as an immortal space-traveling entity.

Perhaps no one else has cable TV and all 200 channels in each country are OTA and there are 200 billion signals floating around;OPerhaps think SETI is simply overmatched unless someone targets us and that signal would still be inroute most likely.

The problem with being unintelligent and a virus is that you die when the host dies, and so you can only ever kill everyone in a small geographically specific area. Global pandemic only became possible with the rise of trading civilizations, but any organism which kills a large % of the population will burn itself out before it can kill all of them.

We worry about disease today because we are trying to do a lot better then middle % survival rates through adulthood.

People with auto-immune diseases aren't less susceptible to being killed by regular infections. That's usually what kills them.

Autoimmune diseases are an interesting problem where for some reason the chemical self/not-self signalling gets messed up, and the immune system starts attacking a host of identified "not self" cells. Other ones - like asthma - are a hypersensitivity of the primary (non-specific) immune response.

Cancer is the exact opposite problem: cancer is when you get a specific series of mutations which do not result in the normal cellular apoptosis mechanism destroying a body cell. The immune system doesn't target cancer because it doesn't target "self" cells. Cancer is immune-invisible, and the holy grail of cancer therapy has always been to find something unique about cancer cells that the immune system can be sensitized to to attack.

None of this is caused by some weird idea of "balance" of the immune system, and the way you used the phrase to start with was a weird thing to do with antibiotics and nature or something.

I suggest thinking hard about your positions before you start advocating withholding treatment from patients and letting people die, which is what you were trying to circumspectively say without sounding like a monster (also looking up the actual causes of antibiotic resistance and how drug-resistance evolves - it's really not what you seem to think).

IF intelligent life is rare and they find us, then you fucking bet they are going to want to visit. We'll be so unusual that other intelligent lifeforms will be compelled just by the fact we exist to check us out and find out what the hell we are. If intelligent life is common, then they'll visit because.... well it's nothing odd so lets say hi to make war or trade.

The simple fact is that if there's intelligent life and they know about us, then they'll be dropping by. Prime directives and shit like that are